Is glass a solid or a liquid? When you see the title, you may say for sure that it is a solid, but in fact, glass is not considered a solid strictly speaking. It is a semi-solid and semi-fluid state with a rather slow flow rate.

Many old church windows in the West that have been used for more than a century are thin on the top and thick on the bottom, which means that when a piece of flat glass is placed vertically for a hundred years, it will become thinner on the top and thicker on the bottom. , Showing liquid properties, which is very similar to the situation where the soap film is thin on the top and thick on the bottom due to gravity. In fact, many popular science books and TV popular science propaganda have talked about this popular science knowledge, which is nothing new.

Glass is not entirely solid

Glass is neither crystalline nor amorphous, nor is it polycrystalline, nor is it a mixed state. The theoretical name is glass state. The characteristic of the glassy state at room temperature is: short-range order, that is, in the range of several or tens of atoms, the atoms are arranged in an orderly manner, showing the characteristics of crystals. Long-range disorder, that is, after increasing the number of atoms, it becomes a disordered arrangement state, and the degree of chaos is similar to liquid. Macroscopically, glass is a solid substance. Glass is such a substance. The reason for this structure of glass is that the viscosity of glass changes too fast with temperature, and the crystallization speed is too slow. When the temperature drops and the crystallization just begins, the viscosity has become very large, and the movement of atoms is restricted, causing this result. Therefore, the glass state is similar to the solid liquid, and the atoms in the substance are always in the process of crystallization.

Therefore, the positions of the atoms in the glass seem to be fixed, but there are still forces between the atoms to make it have a tendency to rearrange. It is not a stable state, which is different from the atomic state in paraffin wax. Therefore, it is also not a crystal. At room temperature, paraffin wax is completely solid, while glass can be regarded as a liquid with high viscosity.

Reveal the mystery of glass non-solid

In the experiment, the researchers used larger colloidal particles to simulate the atoms in order to observe the real movement of the microscopic atoms and observed them with a high-power microscope. It turned out that the gel formed by these particles could not form crystals because of the icosahedral structure-which is consistent with the prediction made by Charles Frank of the University of Bristol in the 1950s. This structure explains why glass is "glass" rather than liquid or solid.

This research is a major breakthrough for understanding metastable materials, and it will make it possible to further develop new materials such as metallic glass. In addition, if the metal can be operated to form a glass-like internal structure when it is cooled, it will be possible to greatly reduce metal defects.

Some materials form crystals when they are cooled, and their atoms are arranged in a highly regular pattern called a "lattice." However, when the glass is cooled, the atoms are crowded together and arranged almost randomly, preventing the formation of a regular lattice.